Quoth Solar:

@alecmuffett bcrypt’s length limit is 72, not 55. The latter is an error originating from Blowfish’s 448-bit recommended maximum key size.

— Solar Designer (@solardiz) November 14, 2012

I found the “55” number in some white paper but I was shocked at how hard it was to get any info on max plaintext length.

Cryppies evidently care more about the entropy than advertising their length.

…now I shall go backpatch my articles.